Professional Football Researchers Association Forum
PFRA is a nonprofit organization dedicated to the history of professional football. Formed in 1979, PFRA members include many of the game's foremost historians and writers.
Mark Rypien in 1991 can easily come to one's mind but there's also his overlooked/forgotten '89 campaign (Wash not making playoffs but he making Pro Bowl albeit as a reserve).
I think Charles White is a unique one-hit wonder when he led the NFL in rushing in 1987, due to his age. He was a star at USC, high pick by the Browns, had some issues, was backup on the Rams for a few years, then had his big 1987 season when Dickerson was traded to Indy. White lost his starting job to Greg Bell in 1988 and was then out of the league for good.